Photographic developer



Patented Sept. 10, 1946 PHOTOGRAPHIC DEVELOPER,

. Frederic R. Bean, Rochester, N. Y., assignor to Eastman Kodak CompanyRooheSter, N. Y., a;

corporation of New Jersey No Drawing. Application March 3, 1945, SerialNo. 580,925

2 Claims. 1

This invention relates to photographic developers, and more particularlyto developers in which the usual alkalies are replaced by a compositionnew for the purpose.

One object of my invention is to provide an airstable,moisture-resistant alkali for use in photographic developers. Anotherobject is to provide an alkali which will give, in photographicdevelopers, approximately the same alkalinity and results as sodiumhydroxide. Another object is to provide a stable, noncaking,ready-mixed, dry developer powder. Still another object is to provide astable, non-caking, ready-mixed, single dry developer powder. Otherobjects will hereinafter appear.

Alkaline developers have been known and used for many years. Thesedevelopers usually contain developing agents, a so-called preservative,such as sodium sulfite, and an alkali. One of the oldest and most usefulalkalies used'in photographic developers is sodium hydroxide, otherwiseknown as caustic soda. The degree of alkalinity which it confers upon adeveloper has been found to be most suitable for certain purposes.However, sodium hydroxide is deliquescent and corrosive, and for thisreason is difiicult to handle, weigh, store and package. Moreover, whenused in ready-mixed, packaged developer powders, which, because of theirconvenience and uniformity, are very popular among both amateur andprofessional photographers, sodium hydroxide is apt to cause caking,discoloration and deterioration of the powder. This rendersimpracticable the preparation of a single-powder developer containingsodium hydroxide.

I have discovered that a mixture of equimolecular proportions of sodiumsulfite and sodium anhydroiormaldehyde sulfanilate is suitable for use Iin photographic developers in which it is desired to have the alkalineproperties of sodium hydroxide without its undesirable properties.

Sodium anhydroformaldehyde sulfanilate has the structural formula SOaNaand may be prepared as follows:

Example 1. 231 g. of sodium sulfanilate were mixed with '75 g. of a 40%aqueous solution of formaldehyde. On warming to 90-100 0., a

2 glassy liquid was formed in about 3045 minutes. It was spread out anddried in a thin layer at 40 C. The product was ground to a white powderwhich was completely stable under ordinary atmospheric conditions. Theyield was practically quantitative.

A mixture of anhydroformaldehyde sulfanilate and sodium sulfite isstable and non-deliquescent, and does not absorb carbon dioxide from theair. It can be weighed, stored and handled with ease. When this mixtureis dissolved in water, the following reaction takes place:

EH; $HaSOaNa N NH NarSOa H10 O NaOH SOaNa SO3NB.

The pH of a solution made by dissolving a grammole of sodiumanhydroformaldehyde sulfanilate and a gram-mole of sodium sulfite in agiven amount of water is practically the same as that of a solution madeby dissolving a gram-mole of sodium hydroxide in the same amount ofwater. An equimolecular mixture of sodium anhydroformaldehydesulfanilate and sodium sulfite can be used in place of sodium hydroxide,333 parts by weight of the mixture replacing 40 parts by weight ofsodium hydroxide, in all photographic developer formulae in which sodiumhydroxide is specified.

The compound S OaNa formed when the mixture of sodiumanhydroformaldehyde sulfanilate and sodium sulfite is dissolved in wateracts as a moderately strong stabilizing agent for alkaline solutions ofphotographic developers. It also exerts a restraining action onphotographic development. Therefore, a developer made up with thismixture shows less photographic activity than one made up with anequivalent amount of sodium hydroxide even though the pH is the same inboth cases.

An equimolecular. mixture of sodium anhydroformaldehyde sulfanilate andsodium sulfite can be used to prepare single-powder developers, since itdoes not react upon the other dry chemicals present in the powder. Itwill be understood that additional sodium sulfite beyond that requiredto make an equimolecular mixture with the sodium anhydroformaldehydesulfanilate may be, and usuall will be, employed in the developer, toperform its usual function as a preservative.

As an example of a single-powder developer containing my novel mixture,I give the following:

p Example 2 Hydroquinone -.g. 6. 0 I r Elon .g l. 5 For use dlssolve in300 m1. of Sodium sulfite g 24.0 Water at about 125 F. (5(1 Sodiumanhydrofor ald hyde 0.); cool to temperature sulfanilate g.. 26.0requisite for use. Potassium bromide g l. O

This developer has all ingredients mixed inti amlate and. sodiumsulfite.

mately together in a single container and remains stable in dry form;without discoloration.

What I claim as my invention and desire to be secured by Letters Patentof the United States is:

1. A photographic developer, in dry form, containing a developing agentand, as an alkali, a mixture, in equimolecular amounts, of sodiumanhydroformaldehyde sulfanilate and sodium sulfite.

2. A photographic developer in the form of a single dry powder,containing a developing agent FREDERIC R. BEAN.

